Signaling system



April 1&6, 1946. w. s. HALsTEAD SIGNALING SYSTEM Filed Sept. 16, 1944 Illll l l l 1. l n.

m24'. EME/EIR April 16, 1946. w.; s. HALSTEAD 2,393,741

SIGNALING SYSTEM Filed Sept. 16 i G ShBStS-Sheei'. 2

April 16,- 1946.

W, S. HALSTEAD SIGNALING SYSTEM Filed Sept. 16, 1944 6 Sheets-Sheet 3 yl/QTRANSMITTER SOCHECK LICHT I y TRANSMITTER' CARRIER p'l-OT RELAY OPERATEO RRE? @tu 47 YPILOT M' IH- HANG-UP /60 l 57 BOX 45 MONITOR TWO CHANNEL RECTIFIER RECEIVER A Y swITCH I e5 H52 44 .5e

ANTENNA POWER TRANSFER TRANSFER RELAY RELAY L L 52 wAYsIOE 49 48 f CONOUCTORS r 55 Y ,"--f--Q-i-R/SA- TRANSMITTER I HANOsI-:T AO/ TONE AUTOMATIC GENERATOR 'PUl-S-NG FIG. 3

CENTRAL STATION UNIT WILLIAM sIIIALsT EAD NVENTOR 9g AT i ERNEY April 16, 1946.

w. s. HALsTEAp 6 Sheets-Sheet 4 .23 1MP/Maul MZON.

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, WKOPUDDZOU mnrw kalm-m Y *Mmm WILLIAM S. HALSTEAD INVENTOR ATTORNEY April 16 1946.

V, w. s. HALsTEAD S IGNALING SYSTEM Filed sept. 16, 1944 @Smets-s115615 6T HAN FIG. 6 I MOBILE uNlT OPTIONAL.

OHECKLIOHT Y' |05 l HALSTEAD INVENTOR A S.. www m Em... L I E I y l NAR l 2 AR W 4 mw T 3 L Q O I A/ LT n n RcD. Y, Mm m E mmm. AN w RRE I `Uur..- CP 0%. A O W R 1 T w Rm 1mm um Duu T WNL. AQL OAE. E .r PRR m T FIO 5 I* MOBILE UNIT A ATTORNEY Patented Apr. 16, 1946 UNITED STATE `attain sIGNAnING SYSTEM William S. Halstead, Purchase, N. Y., asslgnor, by mesne assignments, to Farnsworth Television `8a Radio Corporation, Fort Wayne, Ind., a corporation of Delaware Application September This invention pertains to an inductionradiotelephone system for longitudinally extending traflic lane communications employing wayside 16, 1944, sena1N.554,439 y l 11 claims. (ci. 1791-82) wires, adjacent railway trackageor highways, as

transmission media for establishing long-distance two-way communications between` mobileunits, fixed wayside points and mobile units, or between fixed wayside points.

The system of the invention alsoutilizes a single automatic repeater or an automatic relay group extending in a longitudinal directonalong a `traiiic lane comprising a plurality of zone transmitters and receivers `disposed at'strategiczone control points along the trahie lane, with means for utilizing the zone transmitters and receivers as automatic repeaters under carrier control from a centralpoint, or operable under localized zone control. In this manner, the longitudinal radiotelephone network is divided into an additional zone or a series of zones, each under local control and/or centralized control. The repeaters are instrumental in extending theeffective` induction field surrounding the Wayside wires over required longitudinal distances with respect to the trail'lc lanes, while the amount of carrier signal energy impressed on wayside wires in each zone may be limited to effect the necessary restriction in the lateral extension ofthe field. The system` differs from conventional carrier-current lsystems Vor ordinary induction telephone Asystems inthat no physical connections need bemade to Wayside wire circuits, mobile'units may establish communications over long distances via induction radio signals impressed on wayside wires and an associated repeater or repeaters, no matching networks are utilized, signals are impressed in phase on all wayside circuits, suchas telephone, telegraph and electric power lines, and the combined induction and radiation fields surrounding wayside conductors or loop inductors are employed for two-Way signaling purposes.

In general, the system employs al central station transmitter wherein carrier signals are generated, thence modulated and applied tothe distributing media so that. it may be received, and repeated if desired by a single repeater or a plu-4 rality of zone repeater stations, each oflwhich transmits the signal on a frequency different from that used by the preceding transmitter, The

\zone station may also be used as a local control station, with local or remote microphone and loudspeaker, without acting asa repeater,

Byutilizing such retransmission of signals on different frequencies in alternate-.signaling 'areas or zones, and by the use of frequency modulation transmitters and receivers, the system vis capable of` propagating ,i thef original signal through a substantially indefinite distance wherever-a suitable Vmetallic-path transmission medium or- Vdistributing network is available regardless of whetherthe signal originates at the cenl tral station, from one of the zone' transmitters,

or from a mobile unit. The repeater transmitters may also be used for "zone communications. By using the repeaterstations as set forth herein, any mobile unit, such aspatrain,` truck, bus, i

or other vehicleV can be inconstant communication with a centralstation, a. local zone control station, or with other vehicles. l

An important, distinction between a conven- "tional space radio system and theV induction radio system of'this invention residesin the fact that where wayside wires are present radifre- 'quency signalenergy is required to travelthrough ether, as a transmission" medium, only for the relatively short distance between the mobile unit and the Wayside wires, which then serve asfa transmission medium along the traflic lane. For vehicle to vehiclecommunication', for example, inductionradio signals do not have to directly bridge the airline=distance between the two units, which may be many mi1es,*but travel from one mobile unit to,adjacent wayside wires,- then along the wires,` and thence to the second mobile unit. By means of a repeater associated with these wires the signals from the mobile units may be retransmitted at much higher level, thereby `over-riding noise levels. In this process, which ythe same line,V utilizing a second frequency for this purpose. The intense induction-radio field surrounding Vthe wayside wires is then used-by a second mobile unitv adjacent the wires in recep- "tion off the signals. .In this manner, and by a reversal Vof process so that signals from the second unit are `transmitted `back through the repeater circuits, effective two-way communication may be established, .even though extremely low-V power transmitters and relatively insensitive receivers are used on the mobile units. It is pointed out that the repeaterV station .used in the `process may be a telephone substation or exchange `'where interconnections withtelephone lines orspace radio'circuitsmaybemade.

receivers capable of receiving the central sta-v tion and moblie unit frequencies as well as the automatic repeater frequencies.v The zone receiver used in the automatic repeater equipment may be either of the dual or single channel type depending upon whether the system requires only in the transmission media from the R. F. induction cable will be in phase and of substantially equal intensity in the various wires cf the transmission media, thus increasing the emciency of the system in some instances by having the signal which istransmitted through the transmission media in phase in all of the conductors of the transmission media, and thereby reducing the attenuation in the Vtransmisnsinn line which in turn permits a reduction in signal intensity at the transmitter. However, this might not be the case in the event the signal impressed upon the a single automatic repeater equipment or a mulf tiple of zone repeaters which may be arranged in cascade or tributary connection with respect to a longitudinally-extending wire network, inorder to cover ak desired length of railway or highway transmission media was not in phase in the various `conductors thereof.

` A further object of the invention is to provide a communications system employing wayside t conductors or the like as a transmission media in conjunction with a plurality of relay stations,

system.` To enable the fixed-station network and allucooperating mobile units to operate on the Y safe-fail principle, which is substantially equivalent tothe closed-circuit type of supervision onl conventionalsignali'ng systems employing metalsends out a master checking pulse over the Vdistributing network, which pulse is received at the repeater stations as well as in the mobile unit or units. In this mannerthe repeaters retransmit the test pulse along'the relay network. AY

pulse-actuated check v,light is provided at each of the repeater stations so that the proper operation of the system may constantly be made known to the operators at all iixe'd stations as well as mobile units. e y

At the central station there is also a transmitter .check light which is connected with a monitor receiver so that there maybe a check on the operation of the transmitter at the central station to indicate that the signal is being impressed upon the distributing media.

One object of the present invention is the provisionv of a traiiic control system in which the initialsignal is repeated non-interferingly by an automatic repeater or by a multiple of automatic repeaters distributed throughout the system.

Another object of the present invention is the utilization of the wayside conductors inductively to permit one ormore successive repeat signals to be projected from an initiating point along the system with no interference between'signals from adjacent repeater stations.

yStill another object of the present invention is the utilization of a right-of-way to be divided into one or more'zones and the wayside conductors paralleling such right-of-way, so that a signal initiated in one zone is successivelyV received and repeated along the system to provide a noninterference signal system along the right-ofway. l

Another objectof the present invention is the utilization of one or more automatic repeaters i to pick up and relay signals from one or more mobile units to the central control point or to provide communication between two or more mobile units by means of one or more automatic repeater units along vthe right-oi-way.

A further object of the invention is to provide anR. F. induction cable transmission-line disposed substantially parallel. with and adjacent the wayside wires or otherv conductors of the transmission media, so that the signal induced each consisting of at least one transmitter and one receiver for communications between relay stations disposed adjacent the transmission Vmedia along a traffic lane'and mobile umts on .peater types the traiic lane, each of said relaylrepeater stations, mobile units,-and a central control station having aural transducers and/or visual indicatorsffcr receiving test pulses transmitted from a central control station to provide an audiovisual supervisory means for the safe-fail type to test the integrity of the system at all times. A further object of the'invention is to provide a communications system of the class described employing a metallic Atransmission media disposed along a trafc lane with a central station employing at least one transmitter and one receiver, and atleast one repeater relay station employing at least one transmitter and one receiver,"in conjunction with equipment on a mobile unit which utilizes at least one transmitter and onereceiver so that at all times communication is possible between the central station and the repeater stations and mobile units, or between any combination of mobile units, relay repeater stations, and the central station.

A further object of the invention is to provide a communications system of the class described wherein a signal is impressed from a transmitter on to a metallic transmission mediaV extending along a lane of traflic in such manner that the combined induction and radiation fields surrounding the transmission media will have sumcient signal intensity to provide an adequate signal 'for reception by mobile units substantially within a lateral distance'in feet equivalent to 157,000/f (kc.), where f is the frequency in kilocycles, to the end that the signaling fields surrounding the transmission media are substantially ineffectual in producinga useful or interfering signal at distances in feet greater than 157,000/ f (ka), from the transmission media.

An additional object is the provision of an induction radio-telephone signaling system for use substantially in a longitudinal direction along extended trafiic lanes 'over long distances wherein a strong signal may be provided in all mobile units on or adjacent said'lanes at all points regardless of existence of localized areas in which underground conduit, underwater cables, tunnels, or bridgesmay render ordinary non-reof induction radio systems ineffective. 1

In the drawings:

Fig. 1 is a block diagram showing a trafllc lane communications system with a central stations unit and an automatic repeater station unit.

Fig. 2 is a block diagram showing a traflic lane larly\blo`ck diagram Fig. lthereof, numerblil of a" mobile unit employing a loop'for pickup from the `wayside wires, and transmission thereto. Fig. 6 shows a block diagram of a mobile Iunit with a whip antennaV as an optional methodbf pickup, or transmission;

" Fig. l is a schematic diagram of a'radio yfrequencyfinductionicable transmissionline as used by a central station or repeater; transmitter-unit.

vWith reference to the'drawings and particudesigrtes the existing wayside conductors` run\ ning parallel to the tramclanes |52. The illustrative central station equipment may consist of a receiver or receivers |53, `suchpas isshown in my copending application V.Serial No. 548,962,`re ceptive to frequencies Fi and F2,"a-loudspeaker r |54, apulse lock-out relay |56, `a received carrier pilot |59, a single channel transmitter |51, such as is shown `in my copending application Serial No. 548,962,0perating* on frequency FI having coupled to it a microphone |58, an automatic pulsing unit |60,`and .a tone'generator |6I. The radio `frequency output from` the'transmitter |51 -may be coupled through an RIF. attenuator"|63 to the transfer relay |64. The R. FQ input tothe receiver |53 may also be coupled to the transfer relay |64 so that When'the above-mentioned relay is in receive" position, an R. F. induction cable |65 is connected to said receiver; `The R. F. induction cable |65 usually extends for a distance of from 500 to 1000 feet parallel and in closep'roximity to the wayside conductors |5| andin some instances terminates in terminating 4uniti||56. In llieu of the induction cable coupling means, a line coupling=condenser |65A may be used between lthe transfer relay` |64' and wire circuitsl5l. i Y

The automaticrepeater vunit consists of -a receiving antenna |1|l running parallel to the wayside conductors |5| and connecting to a zone receiver |10, said receiver being responsive,-forl example, to frequency FI. In lieuo'f the receiv ing antenna, a line coupling condenser |1|A may be used between the input of zone receiver |10 and' Wayside wires |5I. The" zone receiver` |10 Y has an audio output connecting to the` loudi speaker and to thezone transmitter |16. `An

additional output from the zone receiver connects to the carrier operated relay |14 which in turn automatically controls the operation of the zone transmitterV |16 whenever a signal is f,re,

ceiyed 4on the receiver |10. The R. F. output `'rho mobile una las coupled to the loop las, in this illustrativeexample, is equipped withatwochannel receivertuned' to frequencies Fl, and F2, u

and a transmitter tuned rtofrequency Fl. A li i `In the operation of theabovedescribed units,

the. use of the single repeater allows the system l to have an extended `rangeof twice that of, `the central stationequipment without a repeater. When the inoloileunit, isinthe central station Fl. When the mobile unit is in the automatic repeater zone, the-Fi signals from ,the central station'or the mobile unit, as thelcase maybe, l5 areY automatically `received by the 1wzone-receiver on FI and automaticallyrepeatedon frequency F2, by the zone transmitter. c \Yhere wayside wiresgxlii `mayleave overhead po essand `go underground in conduit, or enter 2o lead sheatlnngpr where-wayside wires leave traffic lanes and run overhllrlhile the traffic lane goes through a tunnel, supplementary-wires, such as v|40Fi g. 2, may betinductivelynr capacitively` f'cpupled.` to2-wayside wiresawhere they approach the--pointswhere the wires leave the vicinity.V of the travel lane for a short distance go into sheathing, or enter underground por underwater cables. At these points, the supplementary wire maybe coupledgto one `or more existing wayside wires, by capacitors |4| and |42, or 'by induction. coupling in which the supplementary wireis simply disposed inth'e vicinity of` the existingwayside conductors. The supplementary wire thenbridges` the. gap in whichthe existing Wayside` Wiresare ineffectiveior induction radio purposes.

Asv boththe central station andthe automatic repeater units `of the illustrative application -of lights I4, said central-stationunit operatingin` an areaspecied aszoneL- A radioifrequency induction cable transmissionvk line I5 connectsto the RF output terminals of the said central station unit andextendsfo'ra distance of' from'500 vfeet to 1,000 feet parallel to and in close proximity to the wayside conductors |6," and terminatesin the terminating unitll, said RF induccirctnother'zmgpansmitter ne which may m'tion' cable'transmissionline being used for recepthe R. F. attenuatorunit |11 to the radio frequency induction cable |80 which in` turn'runs parallel to the wayside conductors |5| and terminates, in this illustrativev application, in terminating unit IBI..` Theuoutput circuit of the zone transmitter |16 may also be connected through a line coupling condenser 80A, towayside wires |`5| in instances where the induction cable is not used. The microphone |82-, which `of course may be any distance away, is provided for the local operation of the repeater equipment and the checkA light|84 is provided toindicate that the receiver andy carrier operated relay are functioning properly. o

zone, signals can be transmitted between the mobile unit and the, centraistation on frequency r tion as well as transmission ofsignais at the of the Zone receiver next in transfer of energytakes place between the loop- 20 and the Wayside conductors I6, vor vice versa. Zone repeater units are located at zone control l points along the Ytraiiic lane as illustrated by zone 2 repeater 22, consisting of a combined two-channel Areceiver Vand-a two-channel transmitter with associated controls, operating on\'frequencies FI and F2. Coupled to said""zone repeater for local control is a microphone 23, a loudspeaker 24, and 'a check light 25. Means for coupling the repeater 22 to the wayside conductors I6 are providedby the reeciving antenna 26iand the RF induction cable ltransmission line 21 "ending in the terminating unit v28, said receiving antenna and transmission line extending parallel to and in close proximity to'the wayside conductors; I6.`

Other similar zone repeaters are installed 'at various points along'the traflic lane as required, the

"determining factor for spacing between installations normally being governed by the amount of signal'attenuation -along'the railroad right of way or traflic lane,l as the case may be, the desirability of the installation of a zone repeater 'at certain strategic control points, orthe necessity for signal reinforcement at points where wayside power transfer relay 48 which\controls the oper ation of the transmitter 40 and the receiver 44,

ialso controlling vthe antenna transfer relay 49,Ythe automatic musing una n2 and the transmitter pilot light U.

.The handset-52 consistsof a microphone\5-3,`a

push-to-ta'llr` switchv 54.\ nd an ear phone 55.

ceiver of zone.3 repeater 29 receives the signal on frequency F2 and automatically retransmits the signal by means of its associated repeater,-oper atingV on frequency FI orother suitable frequency. Y

Thus it is seen that alternatevstationsoperate on alternate or differing-frequenciesA automatically retransmitting the originating signal along the entire circuit.V y Y Due to theY fact thatrfrequen'cy modulation v,is employed, as describedhereafter, and'that the stronger or initiating signal assumescontrol with originalcontrolling signal will maintain control Vchannel receiver 44 connects to the loud speaker 45, the handsetf52 and the carrier-operated relay 46, contacts ofthe said carrier-operated relay connecting tothe received carrier pilct'light 41 lwhich indicates visually-the presence of an incoming signal. The carrier-operated relay'46 line but not in the When not in use the' han et 52 is placed on a hook or a hang-up box 56 in ywhich position the switch 51 connects the loudspeaker 45 tothe twochannel receiver 44. When the handset 52 is removed from the hook or the hang-up box 56, the switch 51 opens, thereby disconnecting the loudspeaker 45 from the receiver 44. vThe dispatcher orroperator is then in control of the central station unit with the earphone 55 connected to the receiver 44. When the push-to-talk switch 54 is pressed,the power transfer relay 48 and the antenna transfer relay 49 are closed, thereby .transferring the RF .induction cable 60 from the receiver 44 to the transmitter 40. At the same time the automatic pulsing unit 142V is made inoperative, the transmitter pilot light 50 is turned on and the two-channel receiver 44 is made inoperative. Upon Acompleting the message the push-to-talk switch54 isreleased by the operator causing the power transferrelay 48 and the antenna transfer 'relay 4B to open, resulting in connecting the RF induction cable 60 back to the two-channel receiver 44, placing the said receiver in operation, turning off the transmitter pilot light 5|] and again starting the 'operation of the automatic pulsing unit 42. Y Y

The automatic pulsing unit 42 controls the power transfer relay 45 in the samemannery as when the pushto-talk switch 54 is closed ex- Y cept that the tone generator pulse is transmitted over the circuit instead of the voice.

A monitor rectifier 62 coupled to a relay 63, said relay operating the transmitter check light 64 is coupled to the RF output of the transmitter 4D by pick-,up lead 65 to indicate that the transmitter is functioning properly.

In Fig. 4 a dualY channel zone repeater station is indicated in a block diagram form. A twochannel receiver which for clarity is shownas two receivers 1I and 12 adjusted to frequencies Fl and F2 respectively, is coupled to the receivingY antenna 13, said `receiving antenna running parallel and in close proximity to the wayside rconductors 14.V The dual channel receiver outputs'connect to their respective associated car.

g rier operated relays 15 and 16, which in turn control the operation of the transmitters 11 and 18,4

the transfer relay and the check lights 83 and 84. The transfer relay B0 connects to the RF induction cable 8 l, said cable running parallel and in close proximity to the wayside conductors for a distance of from 500 to 1000 feet and terminating in the terminating unit 82.

Associatedwith the zone repeater is a loudspeaker and a local microphone 86 to be used when local control of the zone repeater is desired. The microphone 86 controls the transmitter of the frequency desired. y

In'the operation of thezone'repeater, an incoming signal on Fl receiver 1l controls its associated carrier operated relay 15 so that it operates both the transfer relay 8l] and the transmitter 11 resulting in automatically repeating the signal on also controls' the automatic pulsing unit 42 by 7l frequency F2 back through the RF induction signal on frequencyFl.

sage or'reply to a message originating at the central station or Vzone repeater, the press-to-talk- I switch ||4 on thehandset I|0 is,closed,..result 40 .cable 8| andthene Vinto thewaysi'de conductors` 14.* At the,Sametime itioirolsthe ,Operation ofthe vcheca ughpfs'a indie "ting" that the: repeater l is in operation and blockfslthegreceiver "12' which picked up bythe receiver 12, thecarrier operatedrelay16 controlsvthe transmitter 18 and connects the said` transmitter 18 through thetrans- 10 fer relay 80` to the RF induction cable 8 I, resulting in automatically repeating the incoming F2 At the same time other functions including the operation .of the checkv light 84 are'carried out in the manner outlined 15 in the operation of the repeater with anincoming signalonFl. i y .f

Fig. 5 shows a block, diagram ofr one form kof the mobile unit equipment employing a loop for induction pickup from the waysideonductors 20 and consists of aloop4 IOI coupled through an antenna transfer ,relay |02 to a two channel receiver i |03. A carrier operated rrelay |04 also* connects the receiver |03, contacts of said carrier operated relay |04 operatinga check light25 |05. The check light |05 operates when short pulses are transmitted from the central station and is used as a constantcheck on the operation of the circuit. x The audio output fromthe dual receiver |03 passesthrough the audio fre- 30. I e l A points as, mayYberequiredatsignaiattenuated quency iilter |06 `,which filters out most of the pulsefrequency so that vit will lnot be objectionable to the operator but passes the voice vfrequenciesto the loudspeaker |01 and the earphone |08. The antenna transferrelay |021is normally` in the receiving position. i g ,i When the operator desires `to transmita 'mesing in the operation of the power transferv relayv and the antenna transfer relayl|i2. vThe power transfer relay then shifts the receiver |03 to' an inoperative position and at the same time places the transmitter ||2 `inoperation on i5` frequency F2. 'In the transmitting position, the antenna transfer-,relay |02 connectstheftransmitter ||2 to theloop |0| and the operator can then transmit his message through the. microphone ||5. to-talk switch I I4 themobile unit is again placed in the receiving position so that frequencies FI and F2 maybe received.v

Fig. 6 shows a block diagram oi an identical i.' Y mobile unit equipment except that a whip an- 55 tenna ||8 is employed in place of aloop as `an.

optional .method 'A for pickup from the wayside f conductors. i

Fig. '7 shows an RF induction line transmission conductor or cable |25 as an eiiicient means of s0 couplinga transmitter |26 to the wayside conductor'slZ-T, said RF 4induction cable transmission line `|25 vrunning for a distance `of from 500 to 1000ffe`et parallel' and in close proximityto the,

minationunit 130. The transmission cable |25 to eliminate.A standing. waves .in the RF'ijinducacentralstation. ncludinga le side conductors andoperative .carrier frequencies, a

f means whereby aj 'receive'dvsign By releasing the button on the press- .50V

'coupling' is :toemploy a .transmission line |25`as a loopof extremely long'top and bottom sections with wide .spacing between ground return fand i thehigh side of the loop,the far endfof which may `be-grounded as shown tl |34. loop'ds in` a, vertical plane, `parallel to theiraflic lane.` The lowerside of the loopcan be a. wire, a1ls'teel rail, afpperor :equivalent conductorlrunninig'parallel to the waysideconductors andgroundedat the -far end, `asindicated. l

In either system of coupling the ransmitter to the wayside' f conductors, therradio'zfreqllnfy attenuator |28 allows the outputY of ,thetrans- Vmittel' `|26 to be adjusted to suchea" value that the lateral extension of .the inductie can be `maintained within desired limits.

From the foregoing descriptio 4 junction .with the drawings, itevident that there is providedgatramc lane'comn micating system thatensuresag'a'nst interfere e and tends -to i assuredesired signaling from to the other suceessiv ind successfully it wm. be appreeiatedrr'am; the, :menge forthf in, which repeater lunitsgaijejusedj detrpmmeelreege 'the 0f Way. divided zones, wayside conductors along he right LofAvvay, transmitter and receiverinductivelyfassociate Vth e e remainder-dated ed a zone transmitti'giand receiving' relay unit4 inducttiveli1V y associatedwith said waysidecondctofsgisaiqreiay unir-inducing rier frequency characteristic 1s a' different carrier frquenfy'feiaracteristicfinan l the received signal,saidfretransmitted sigaalfbeing inductively "imposedbaclj ontoythe `wayside conductorawith vthe same 'modulation' characn teristics as originally impressed Aup'onfthe `signal 'at said centralstation. f

f2." In a trame lcommunications.5system Ainaving Va y'primary signalingvr zonee tending alc'ig afright [jfV way dividerifinto secondarysignaling. zones,

wayside conductors alongthe right of wayfa cen- "tra'lstationincluding-at least atransmitter and receiver of modulated 'carrierfrequencies inductively Vassociated 'with saidways'ide` conductors, and a'plurality` of'zone transmitting and'receivingrelay unitsindu'ctively associatedfwith said wayside conductors, eachof said relay-units inwayside'coriductors |21 andsterminatingin ater- 05 cliidng meanswhereb'yareceivedsignali-having `onecarrier frequency characteristic ylis f transniitted' at'adiferent carrier frequency-:characteristic -Vthairithe'received signal `andindnctively imposed back` onto the wayside conductors, both said received and said.re-transmitted` carrier signals having substantially the same.- modulation characteristics;

' 3. #In `a 'traffic communieations1 `having i a-primarysignaling zone extendingfalollg right.

:tion-:cable transmission* line by .matchingthe :'f'tofway which is dividedrinto secondary signaling zones, wayside conductors extending*along-the?vl right of way of sufclent distance to embrace. the primary signaling zone, a centralstation including at least a transmitter. and receiver of modulated carrier frequencies inductively associated.

with said wayside conductors, and a plurality of relay units having transmitting and receiving means therein inductively associated with said wayside conductors, each of said relayunits including apparatus for receiving a signal on one carrier frequency and retransmitting said received signal on a different carrier frequency, said relay units disposed along said right-of-way each vtransmitting its received signal on a car- .rler frequency d ierent than the transmitter in its adjacent zone on either side thereof, said respective carriers all bearing substantially. identical modulation characteristics, whereby intelli- Y tiating induction radio Signals at one carrier frequency, the said carrier signal means being inductively coupled with said wayside conductors,

and a plurality of signal receiving and `a transmitting means disposed at secondary signaling zones along said right-of-way, said receiving and transmitting means being employed in each secondary zone for receivingand successively-re peating the initiated signals along said right-ofway, each signal receiving and repeating means being inductively associated with the wayside conductors, the repeating means also being capableof originating carrier signals, the signal thus initiated being alternately repeated in successive zones along said right-of-way at dierent carrier frequencies to ensure a non-interfering signal throughput the system.

5. In a traffic communications system having a primary right-of-way signaling zone divided into secondary zones, wayside conductors extending throughout said right-of-way, a primary initiating signal vmeans capable of initiating signals `at one carrier frequency, said 'signal initiating means being inductively coupled with said wayside conductors, a plurality of signal repeating means ldisposed in each of said secondary zones along said right-of-way, for receiving and successively repeating the signal initiated at the primary signal initiating means along said righto-way, each signal repeating means being inductively associated with the wayside conductors, the

repeating means also beingcapable of originating carrier signals, the'signal 'thus initiated by therepeater'means being alternately repeated in successive zones at `diile'rent carrier frequencies to ensure a non-interfering signal throughout the system, and a mobile unit movable along the right-of-way having a two-way radio apparatus a zone repeater for eachof said secondary zones, each repeater including-a receiver and a transmitter inductively coupled-with the wayside conductors, the signals received on one frequency being re-transmitted by the zone transmitter on a different frequency, and a mobile unit movable along the right-of-way having a two-way radio apparatusV carried thereby and being inductively coupled with the wayside conductors to permit two-way radio communication with the central transmitter station and any of said zone repeaters.

' 7. In a trailc communications system having a primary right-of-way signaling zone divided into'secondary zones, wayside conductors along the right-of-way, a central transmitter station in ductively coupled with said wayside conductors, a zone repeater for each of said secondary zones,

i each repeater includingia receiver and a transmitter inductively coupled with the wayside conductors, the signals received on one frequency being re-.transmitted by the zone transmitter on a diierent frequency, and at least two mobile units movable along the right-of-way, each of said mobile units having a two-way radio apparatus carried thereby and being inductively coupled with the wayside conductors to permit two-way radio communication between said mobile units vthrough one or more zonev repeaters.VK

8. In a radiosignaling system effectivein twoway communications with vehicles throughout the length of a longitudinally-extending tramo lane and within a limited lateral distance from wayside conductors normally extending parallel to the traffic lane wayside conductors, a radio relay group for progressive signaling over said wayside conductors along a trafllc lane and disposed in proximity thereto, said relay group consisting of a' plurality oiA carrier wave repeater-stations transfer means" associated with each of saidv transmitters and receivers for utilizing said wayside conductors as `-a transmission medium along trafllc lane substantially within a lateral Adistance said trame lane, whereby the combinedinduction and radiation fields surrounding said wayside conductors are employed in establishing communications with vehicles proceeding along said in feet of 157,000/f (kc) from said wayside con- I ductors, said fields being ineffective in producing an interfering signal at distances in feet greater than 157,000/f (kc) from said wayside conductors.r f

9. In a tramo communications system having a primary signaling zone extending along a rightof-way divided into .secondary signaling zones, 'signal propagating means'associated with said right-oi'way for establishing said primary sigcarried thereby and being inductively coupled with the wayside conductorsto permit two-way radio communication with the initiating signal means and the repeating` means ofthe zone apparatus.

6. In a traflic communications system having a primary right-of-way signalingzone divided into A ductively coupled with said wayside conductors.y

naling zone, a `centralstation including at least a transmitter and receiver operatively associated with said signal propagating'means and Operative .with modulated carrier frequencies, a normally '70 operating check signal source associated with `said central station transmitter 4for applying c check signals on said signal propagating means,

said lsignal propagating means including atleast one zonel receiving and transmittingrelay unit,

n said relay unit includingr` means whereby said lay unit including means whereby check signal is received with -one carrier frequency characteristic andretransmitted with a different carrier` frequency characteristic if said relay unit is operative, and receiving means op-l ter and receiver coupled to said wayside mediumand operative with modulated carrier frequencies, a transmitting and receiving relay unit, means for coupling said relay unit with a conductive portion of said wayside medium, said rel a received signal from either said central station or said mobile station having one carrier frequency characteristic is retransmitted at a different carrier frequency characteristic than the received signal, said retransmitted signal being impressed back onto the said wayside medium with the same -ductive portion modulation characteristics as `originally impressed upon the signal at said central station or said mobile station.

11. In a trame communications system, an electrically continuous wayside signal transmislsion medium, a central station including a transmitter and receiver coupled to said wayside medium and operative with modulated carrier frequencies, a transmitting and receiving relay unit, means for coupling said relay unit with a conof said wayside medium, said relay unit including means whereby a received signal from said central stationhaving one carrier frequency characteristic is retransmitted at a different carrier frequency characteristic than.

the received signal, said retransmittedV signal being impressed back onto' the said wayside medium with thesame modulation characteristics as originally impressed upon the signal at said centrai station and a mobile station including a transmitter and` a multi-channel receiver coupled to said wayside medium, said multi-channel receiver being responsive to all of the modulated carrier frequencies impressed on said wayside medium.

WILLIAM S. HALST'EAD. 

